Shrink film

Abstract

A shrink film comprising a polyethylene film, characterized in that said polyethylene is an ethylene copolymer mixture having a molecular weight distribution in the range 10 to 35, a density of 915 to 940 kg/m 3 , a weight average molecular weight of at least 100000 D and an MFR 2.16 (190° C.) of 0.1 to 0.9 kg/m 3 , which copolymer mixture is produced by a two or more stage copolymerization of ethylene and 2 to 10% mole (relative to ethylene) of a C 3-12 alpha-olefin comonomer in a series of reactors including at least one slurry loop reactor and at least one gas phase reactor using a heterogeneous Ziegler-Natta catalyst.

1. A shrink film comprising a polyethylene film, comprising an ethylene copolymer mixture having a molecular weight distribution in the range 10 to 35, a density of 915 to 940 kg/m 3 , a weight average molecular weight of at least 100000 D and an MFR 2.16  (190° C.) of 0.1 to 0.9 g/10 min, which copolymer mixture is produced by a two or more stage copolymerization of ethylene and 2 to 10% mole (relative to ethylene) of a C 3-12  alpha-olefin comonomer in a series of reactors including at least one slurry loop reactor and at least one gas phase reactor using a heterogeneous Ziegler-Natta catalyst;
 wherein the copolymer mixture is bimodal and comprises a lower molecular weight component and a higher molecular weight component; and wherein the lower molecular weight component has an MFR 2  of at least 100 g/10 min and a density of from 945 kg/m 3  to 960 kg/m 3 . 
 
     
     
       2. A shrink film as claimed in  claim 1  wherein the molecular weight of the copolymer is 150000 to 300000 D. 
     
     
       3. A shrink film as claimed in  claim 1  wherein the molecular weight of the copolymer is at least 226,000 D. 
     
     
       4. A shrink film as claimed in  claim 1  wherein the MWD of the copolymer is between 15 and 23. 
     
     
       5. A shrink film as claimed in  claim 1  wherein said copolymer comprises a lower molecular weight component and a higher molecular weight component both formed from an ethylene/butene copolymer. 
     
     
       6. A shrink film as claimed in  claim 1  wherein the MFR 2  of the copolymer is 0.15 to 0.6 g/10 min. 
     
     
       7. A shrink film as claimed in  claim 1  wherein the value of a films' dart drop (g)/thickness (μm) is at least 4.5. 
     
     
       8. A shrink film as claimed in  claim 1  wherein said film has a thickness of 20 to 120 μm. 
     
     
       9. A shrink film as claimed in  claim 1  wherein said shrink film is a multilayer film. 
     
     
       10. A shrink film as claimed in  claim 1  wherein said shrink film is unilamellar. 
     
     
       11. A shrink film as claimed in  claim 10  having a thickness of 100 to 200 μm. 
     
     
       12. A process for wrapping an object comprising applying a shrink film about said object and shrinking said film by the application of heat thereto, characterized in that said film is a shrink film according to  claim 1 . 
     
     
       13. An object shrink wrapped with a shrink film according to  claim 1 . 
     
     
       14. A polyolefin shrink film as claimed in  claim 1  having a Dart drop value (g)/film thickness (μm) of 5 g/μm or more. 
     
     
       15. The shrink film of  claim 14  wherein Dart drop value (g)/film thickness (μm) is 6 g/μm or more.